HT4100 4.1, 4.5, 4.9 Discussion, 4100 Reliability in Cadillac Engine Technical Discussion; Sometime in the future, I would like to purchase an older Eldorado, or Seville. The '80 - '85 Seville, only ...

4100 Reliability

Sometime in the future, I would like to purchase an older Eldorado, or Seville. The '80 - '85 Seville, only came with the 4100, and the Eldo, from '82 - '85. I have heard many mixed things about the 4100. I figure this is the right place to ask this. Just how reliable is this engine? If I were to get a car, with about 75,000 to 90,000 miles on it, am I looking to rebuild the engine soon after purchasing it? What are it's weak points? I know it is low on horsepower, so that is a given. Thanks for any input that can be given.

Re: 4100 Reliability

the intake manifold is the weak spot. Also the push rods, I think. The upper end is strong and could be supercharged and handle the extra PSI as is, but the torque is great on these engines, and if you wanted it SC'd (like I do) it would involve a whole new engine management system I think. New intake manifolds are hard to find and expensive.

Re: 4100 Reliability

The weakest point on these engines is the head gasket. Keep the coolent up to date, with supplement and it will be fine. The second problem is the cat converter, which tends to plug up. If you are looking at one, check the coolent level and make sure that it is full, and looks good.

You are correct, in that they have no power. I have an '84 Eldo as my daily driver, and I just drive slow. On the plus side, they do get good gas mileage considering the size and the age of the car.

Re: 4100 Reliability

I have to completely disagree with you, Vlrench. These things don't get good gas mileage, are you crazy? I have a rebuilt engine. It runs great. But it's a freakin' V8, how the hell would you get gas mleage? Yeah they're only 4.1 liters, so that helps, but still it's a heavy car.

The head gasket will always blow if you don't keep a motor cool! DUH!

A cat will always wear out! ON ANY CAR! I know many people with '97 and newer BMW 540i's (v8) and the OEM cats always rattle. That's just how you know they're worn out. The rattling is obviously from it falling apart inside.

My HT4100 in a 4-door DeVille (BANANA SLUG of a boat) keeps up with the behemoth SUV's and will dust civics. It's not a slow car. It's not fast, but it is NOT that slow. If only you could get them to wind up and still make something, but they're all low-end. (which is good when you're pushing a banana slug boat)

Re: 4100 Reliability

That engine was never intended to go into such heavy cars. That was done because Cadillac saw an increased demand for large cars. Gas prices stopped climbing and the public was not ready to drive around in soup cans just yet.
I suspect that the HT4100 block which has the Buick/Olds/Pontiac bell housing is inferior in strength to the original design which has a toy transmission bellhousing. The Eldorado/Seville HT4100 engine is identical to the Deville/Fleetwood in years up to 85 (except for 1985 Deville). Later cars used a transverse setup with a different block. Anyone who visited Cadillac dealership parts departments in the mid '80's has seen the piled up crates of warranteed HT4100's headed out. That series of engines did very well in later years but was always a liability when used in the older bodies. Those cars are sure nice and there are still lots of clean examples around. Really a shame but the answer is maybe consider a similar year Buick Riviera which has an Olds engine. A properly converted car would be nice too. A diesel car converted over to gas Olds power is also an option.
Yeah, there are people who do very well with the HT4100 in a 4000 Lb car. Some people start smoking 2 packs a day at age 10 and live to 100 too.

Re: 4100 Reliability

Ape Man

An '84 or '85 Riviera is definitely an option. Also the same era Toronado. Since the only cars I am looking at, that have the 4100 motor, are the Eldo and Seville, I am just trying to feel out the reliability. Since I have already owned an '82 Riviera, I am a little knowledgeable of the trannies. I am going to go out on a limb here, and "ASSUME", that all of these cars shared the same tranny. If this is incorrest, than please correct me.

Re: 4100 Reliability

You might also want to check this out as well. It speaks of swapping the engines from a ht4100 to 403 but it also mentions tranny and engines from the 80-85 Eldo/Seville/Riviera/and Toronado. http://www.eldocountry.com/eldo/index.html

Re: 4100 Reliability

Solidgold,

I think the orginal post was asking about the weak points of the engine, I told him what I know. Yea, I rebuilt one before, and yea I drive one now, so I do have some good knowledge on how these things operate.

A 4,000 pound + car, getting 25 mpg on highway is good gas milage.

As far as the head gasket problem, it has to do with the aluminum block and cast iron heads. They expand and contract at different rates, so they are more prone to head gastket problems than usual engines, unless it is maintained properly...I never heard of push rod problems with these motors. Super charging a front drive Eldo/Seville would be interesting also.

The best alternative, if you don't want the HT4100 would be to find a '79 or '80 Eldo, with the 350 gas engine. Sometimes ebay has some, listed that look reasonable. '81's had the V8-6-4. There are also a few v6 cars, along with the Diesels sprinkled in for good measure during these years.

There is an early 80's Olds toranodo in the town that I live in, that looks brand new. It looks simular to my Eldo styling wise, and would make a good alternative...but I like the Caddy better, ht4100 and all.

Re: 4100 Reliability

I agree that car (which is heavy) is underpowered and at the same token, gets pretty good gas milage.

And while they might have problems, there are many of HT4100 users on this forum who drive cars with those engines. Any engine can have problems and HT4100 is no different. If there weren't any HT4100 owners and drivers, this forum wouldn't exist.

If coolant is changed often, then there should be no problems with head gaskets. Another problem I've heard of is the nylon timing gear stripping teeth in older cars (with milage over 100k). But I think that problem was addressed in newer version of the engine (85 and newer).

I never heard of pushrod issues.

Some cars with HT4100 engines are getting close to being antique vehicles and should be treated as such.

Re: 4100 Reliability

Peteski - thanks for mentioning the "antique" status of these old cars. I don't think they'll ever reach the values of the old muscle cars, but they are very cool and are becoming collectible. Mine's an 83 Coupe DeVille with 116k miles on the original HT4100. It runs great and has proved to be quite durable. I'm due to replace the timing chain and gears, but with that maintenance item complete I expect it to run for years to come and I get compliments every time I take it out.
These engines do require regular maintenance, more so than most engines probably, but they are fine motors if properly cared for (the 82,s were quite problematic, but those issue were mostly resolved by mid 83). EPA rated mileage is 17 city, 25 highway. I think that's OK for the time period.
The tranny (in my rear drive application) is also very reliable given the relatively low output of the engine. A typical tranny problem is the torque converter lock up solenoid, but it's an easy fix and costs about $20. When I did mine last year, I had virtually no metal or clutch dust in the pan and my tranny shifts like new.
I'd buy another HT4100 car without hesitation if I know it's been well maintained. They're cheap now and will always go up in value from here on out. . .

Re: 4100 Reliability

Thanks guys. Considering, that when asking an owner of a potential buy, will always say that they maintained thier car to the letter, and then some, what would be some immediate things to look for, that are engine / tranny specific? Anything specific to these cars, that should not be overlooked? I am a gear head, so checking out a used car, is no issue for me. But, I always find out something about a car, after i buy it. Something that is an inherant problem, to the line of car. This will be the first time that I am actually doing my homework, and getting info, beforehand. I am just trying to limit my chances of buying somebody elses headache.

Re: 4100 Reliability

Get the car on a lift and check for worn out front end parts. $$$$$$$. Ck tire wear patterns. Ask the guy how many miles he gets out of a set of tires.
Check the emergency brake. Does the pedal have resistance like it should or does it just flounder all the way to the floor. Test drive the service brake. Pedal feel? pulsation? $$$$$$ Rear dics brakes can be a real pain.
Look for engine leaks. Check the condition of the radiator. See if there are barnicles growing inside on the tubes. $$$$$$ The radiator fan clutch should show some resistance to spinning the fan by hand.
Look at the CV boots. Take it for a ride in a lower gear that has some engine braking and put your foot on and off the gas. See if there is any driveline slack which will make a clunk. $$$$$
Ck the AC. If it has been converted over to R134 then it will not ever be as cold as designed unless the condensor has been changed to a newer style unit. This is almost never done. $$$$$
Depress the off and warmer buttons on the climate control head at the same time with the key in the run position. It will do a segment check then display any codes. It will then stop at 70. $$$$$$
Check for worn out door hinges. Open the driver's door and lift it straight up.
Invite a few fat freinds to sit in the back and see if the auto level works.$$$$
Check the final drive. Any leaks? Any gear noises? $$$$$$$$
Ask the guy what has been done to maintain the engine. If he can produce a service record then check it out especially to see if the engineering screwup bandaid in a blister pack special coolant tablets were used. Joe at Joe's garage might have been changing the coolant all these years without ever knowing about them. $$$$$$$$$$$$$$$$$$$$$$$$$
Listen for ANY signs of bottom end or valvetrain noise from the "engine". Pull the dipstick and carefully look for any signs of coolant in the oil. See if the thing has been doped up with heavy oil like 20w-50 to mask any noises. Check the trans fluid for burnt scent. Some of these only leak small enough amounts of coolant into the crankcase to wipe out the camshaft lobes. The lifters will stop rotating and wear out themselves and the lobe in a very short time. Bottom end noises show up with the engine in gear at idle when hot. $$$$$$$$$$$$$$$$$
You want to find out if the guy's mechanic has advised him to sell it due to a death sentence failure around the corner.
If all this stuff passes then you have a decent chance of staying afloat in the bay.

Re: 4100 Reliability

Yo Ape Man, you didn't need to type all of that. I was trying to save someone (you) the trouble of doing that. I was only interested in the things to look for, for the specific cars in question (Eldo, Riv, Toronado). Issues that these cars have in particular. I am well aware of what to look for, when checking out a used car. Sorry you went through all of that typing, but it is appreciated. Thanks

Re: 4100 Reliability

I always pefer cars where the same person has owned it a long time and has service records showing what's been done. I'd say that's especially important with the HT4100. I don't take their word for it, as they say in Missouri. . ."show me". . .